Modifying for All-Purpose Wheeling

By |2018-05-17T09:27:19+00:00May 1st, 2018|
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Sometimes I feel I’m asking a lot from my everyday manual chair. I want my wheelchair to slip between narrow store aisles and public bathroom stalls as well as push over grassy fields and dirt trails. I want it to be fast enough to take my dog for a run and not be marooned on the sidewalk — feeling the shame of the unprepared owner — when she decides to pop a squat.

There are occasions when having a dedicated off-road chair would be nice, but for everyday use I want to be able to roll off the pavement without having to think about it. Thankfully, with a few modifications, an everyday chair can be versatile enough for the city and the trail.

Casters

Front casters are an important component of rolling over soft ground. Small, narrow casters that come standard on many models of manual wheelchairs are prone to get caught up on small rocks, roots and other protuberances and send you sprawling to the dirt. Changing your front casters is an easy fix to make your everyday chair better equipped for off-road wheeling, but there are a few things you need to consider.

gear hacks wheelchair modificarionsFirst is caster diameter. The bigger the front caster, the more easily it rolls over rough ground and avoids digging into soft surfaces. But putting bigger front casters on your wheelchair will raise your front end, giving the chair more dump. This isn’t necessarily a bad thing for off-road wheeling, as having more dump can give you a more stable base to push from. But anytime you change your seating position, be careful to watch out for skin issues, as sometimes just a small change can lead to big problems.

Also, if you have any camber in your wheels, changing the front-to-rear height ratio will affect your toe in/toe out. This can make your wheels scrub and roll less efficiently. Chairs with one or two degrees of camber won’t be affected noticeably by putting casters that are bigger by an inch on the front, but the more camber you have, the more effect you’ll feel. You can remedy this by either moving your rear seat height up to match bigger wheels and/or tires, or switching to a camber bar or inserts that have zero degrees of camber.

Those fixes beget their own considerations, so if you don’t feel like messing with all that, an easy upgrade is to simply get wider casters that are the same diameters as the ones you currently run. You can get a pair of forks and wide casters from TiLite, FrogLegs and Box Wheelchairs, among others, that start around $200, depending on caster diameter. Even if you don’t increase the diameter, you’ll be amazed at how much better a wide caster rolls over the rough stuff.

Switching casters from standard to wide width reduces obstacles in uneven terrain.

Switching casters from standard to wide width reduces obstacles in uneven terrain.

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Another option is buying a Freewheel 12-inch front wheel attachment, which many wheelers swear by. At a cost of $600 and up depending on style, I think it’s a fine product and have one myself. But my everyday chair setup is functional enough in most off-road environments that I only use the Freewheel if I want to do some serious trekking, like pushing significant distances on surfaces such as gravel or soft dirt.

Tires

Changing to longer axles with spacers (made with wheel bearings) adds more space for knobby tires, so they don’t rub on sideguards or clothing.

Changing to longer axles with spacers (made with wheel bearings) adds more space for knobby tires, so they don’t rub on sideguards or clothing.

If you spend a lot of time rolling off-road, a set of rear wheels with knobby tires are a must. Fortunately, fatter, mountain-bike style tires will fit on a standard width wheelchair wheel, so you shouldn’t need to buy a dedicated set of rims. Most people who’ve been in a chair for any length of time have at least one set of old wheels sitting in a garage or closet. Knobby tires are readily available for standard-size wheelchair wheels of 24, 25 and 26 inches. In my experience, bike shops have better prices and variety than wheelchair specific stores — a basic MTB tire can run you anywhere from $20-40 and up per tire. But be careful with sizing, as 25-inch wheelchair rims take 26-inch mountain bike tires. To avoid confusion, give your shop bike-industry metric sizes — 540mm, 559mm and 590mm, respectively.

Another thing to consider is axle length. Because knobby tires are wider than typical wheelchair tires, they can rub on sideguards or clothing if you have tight clearances between your chair and tires. To solve this, you can use axles that are set slightly longer and use wheel bearings as spacers to keep the knobby tires set wide enough to avoid rubbing. The length of wheelchair axles can be easily adjusted with two adjustable wrenches. If your current axles are set as long as they’ll go, you’ll have to buy longer ones (available through a variety of adaptive equipment retailers).

Knobby tires have a larger outer diameter than regular tires, so if you want to keep your rear seat height the same, you’ll need to mount them on smaller diameter rims than you typically use.

If you want to be super minimalist and have one set of wheels/tires that will function both on pavement and off road, Schwalbe sells its classic Marathon touring tires in a variety of widths. A wider touring tire will provide a cushier off-road ride with some tread for grip, but it will still roll smoothly and fairly efficiently on pavement. Something like a 32-599 — the 32 refers to metric-size tire width — would function well as an all-purpose tire if you use 25-inch wheels.

Seating Position

Center of gravity is a tricky beast — too much and it’s damn easy to flip over backwards, but too little and you’re putting more weight on your front end, making it harder to wheelie and easier for your casters to dig into rough ground. Over my 17 years of being in a wheelchair, I’ve found that I’m able to handle more tippiness than I, or my therapists, ever would have thought. Moving my center of gravity farther back puts me in position to use more wheel when I push, and it also makes my front casters float over small obstacles much more easily. Sidewalk cracks, roots, rocks and gravel — everything is a little easier to roll over when you have more weight on your rear wheels and not on your tiny front casters. A number of manual wheelchairs, like the TiLite TR I use, have an adjustable center of gravity. It can be worth playing with your CG to find the right balance point, something that is both safe and functional for your pushing purposes.

All of these hacks will make a difference on their own. When combined, they should give you the option to transition from pavement to dirt with little, if any, forethought. If you have any questions or comments, please email me at smcbride@unitedspinal.org and we can continue the conversation online.